Re-incarnation is the basis of the Vedic ethos. The theory of Karma is based on re-incarnation. Law of Karma shall have no meaning if there were no re-incarnation. If one had, just one life, how does it matter how one lives? One would then worry, only about rights and not responsibilities. Rights would mean just this; since one has only one life, it would become important just to enjoy and do anything that pleases the senses. Why would anyone care for duties, when you have just one life? Whom do you want to satisfy? Contrary to this quite abject idea, the Vedic ethos tells man “Do not talk of rights, you have none, Talk only about duties.” which makes it binding on us, to probe deeper. This probing shall takes us into the domain of re-incarnation of the soul. If we want a better life, you should have behaved well in a previous life-time. Rights are reserved. Only if duties are executed to the best, there is a possibility that “certain” rights may be awarded, but that too depends on how many times you have been disobedient, to what is appropriate. So re-incarnation sets the basis for our life on this planet.
Fundamentally re-incarnation follows some broad outlines as enunciated by the Vedic writings and as expressed by fully-evolved or God-realized beings known as sages or seers. There are 8.4 million species that represent the various species on earth as well as species of different dimensions, who cannot be perceived by the five senses of humans directly, such as ghosts, goblins, celestial beings and those too of wide, varied nature. Depending on what one has done and what one has not done, appropriate and inappropriate, in line with or against the perfect Vedic injunctions, 8.4 million bodies are possible to be attained by a living entity and each body has a specific life-time, again depending on the law of Karma. Life-force or that entity which i”lives” is universal, it has no respite and lives through these multitudinous bodies. The living entity is the individualized form of the Absolute. Along with it exists the aspect of matter. When these two come together, the living form of plants, animals or humans is the result. The living entities so to say have no age, they are beginningless just like the Absolute. However because of their constant association with matter, the other aspect of the Absolute, there is distortion which differentiates the living entity from the Absolute. Matter, although emerges out of the Absolute, cannot distort the Absolute. In that sense Absolute is the parent of matter but remains undistorted and pure, although matter represents distortion and impurity. That aspect of the Absolute that gets distorted by matter is verily the living entity. The whole panorama of life is the journey of the living entity from almost complete distortion to a state of absolute clarity, realization of the Absolute and attaining oneness with the Absolute.
The philosophy of reincarnating and attaining the human form is explained further. For example, I am a human being, and I am attached to eating, eating from morning to night. I think of food all the time and I take the first opportunity to grab at food and talk to friends about food. I have developed a particular tendency, a certain tendency suiting a particular body, which should ideally not be present in the human body. Now each category of animals has been described in detail in Vedic Scriptures. Now, based on one’s understanding, when I am interested in food, like this, which animal is one reminded of? It is, of course the “hog”. This is the most striking feature of my life, the very basis of my life. But this human body is not meant for eating, mating, sleeping and depending as its primary motive. So a glutton shall obviously re-incarnate as a hog, so say the scriptures. This is done with a good intention, by Nature. We have been given this human body as Grace, as a blessing, for a higher life, for a higher goal. But if this life is wasted after food, Nature becomes particularly kind to the living entity. She says this human body is now wasted, so She gives you another body , where you enjoy “food”, you eat so much, so much more that you become fed up of food, so that there remains no hankering for tasty food. In your prior-previous life-time before you became human, by arrangement of Nature, you could not enjoy food, during the natural course of evolution. You then became human; in that birth, Nature found out you’re interest in food is similar to that of a hog. The hog’s body is suited for eating voraciously. As a human if you eat too much you may get sick, but as a hog, you need not worry about health, the more you eat “whatever”, the more you “enjoy”. Similarly humans overtly engaged with sex, take bodies of monkeys in their next life. Ladies who like to show their bodies, are reborn as trees, so that they get “fed” up, standing at the same place naked for hundreds of years!! and so on. Description of all species and their particular tendencies are found extensively in the Puranas.
The soul is busy transmigrating all the time. For every tiny emotion, Nature has a body for you. For 4.32 billion years you transmigrate through 8.4 million bodies. However when the living entity enters final maturity after going around for millions of Kalpas ( 12 hours of Lord Brahma which is 4.32 billion earth years), intelligence is attained. That is why you may find many intelligent people who may not be known to be particularly spiritual, but are concerned with knowledge and do not simply engage themselves in just eating, mating, sleeping and defending. Out of the 8.4 million species there are about 3 million lower species like ghosts, goblins etc who get that body because of excessive or unfulfilled desire, people who commit suicide and so one, where the suffering is many million times severe than that experienced by humans. Then there are about 1 to 2 million species of the higher planetary systems which science can perhaps never discover, the higher vibratory realms where the enjoyment is many many millions of times higher than what the richest man of earth can ever imagine. Until people realize that the goal of life is neither to go to these upper subtle realms of enjoyment nor try to settle on earth, they go on recycling between the higher realms and earth without rest, if good Karma is stuck to them, which is also reincarnation in a higher subtler body, where pleasure seeking becomes the goal Bad Karma of course, takes them to subtler hellish planets where the soul suffers for many million earth years, the reincarnation is in subtler heavier bodies which undergoes severe pain and yet one does not die or leave that body for millions of years. This is where the concept of liberation comes into being, a dimension of no return. This can be attained only on the earth plane when one gets the rare opportunity of reincarnating as a human that can happen perhaps once in a thousand billion earth years. Of course the higher planetary subtle systems of the Devatas etc are pleasurable but they do not constitute “eternal happiness”, they do not guarantee joy “forever”. Hence based on good Karma , a man of higher reckoning stays for say 70 years on earth and transmigrates a billion times in the higher realms, which Vedic scriptures call as “unfortunate”. The life span of Devatas (celestials) is many many millions of years and the life span of Devatas can range over a few Kalpas, before one gets an opportunity to come down to earth. the scriptures say that even Devatas pine for a human body because they are fed-up of enjoyment and now they desire liberation. Liiberation is only possible through the human body. This is the speciality of being human. Many of the successful people on earth, may do good, but do not aim for liberation and hence they regurgitate between the higher and lower dimensions for several million cycles and never reach to a point of liberation. Liberation becomes the desire of the heart only by the grace of a true sage, when a human associates with a sage, who is already liberated and “appears” on the earthly plane by the will of the Lord, to guide the frustrated soul. Such a person remains liberated forever and is never born or dies like so-called ordinary individuals.
A being only comes to peace and enters the eternal plane, the plane of perfect rest, when one does not have to undergo Karma, after all Karma has been exhausted, when liberation happens. This is the stage of God-realization, the perfectly intuitive state. This state is fully governed by the will of the individual, a power handed over to him by the Absolute post-liberation, in perfect consonance with Divine Will. In this stage the liberated one, shall be relieved of the suffering of birth and death, his appearance or disappearance on the earthly plane shall be, only to help other living entities attain liberation.